The alarming figures are included in the recently published Environmental Protection Agency (EPA) Domestic Waste Water Treatment Systems Inspections Report (2022). Based on 1,143 country-wide inspections (primarily focused near rivers where there is a greater risk to water quality and areas with shallow soils with an increased risk to household wells), the report highlighted that 20 per cent of those septic tanks tested posed a “risk to human health and the environment”. More than half of the failures reported were attributed to inadequate maintenance and desludging of septic tanks.

The Rivers Trust Ireland Development Manager Constanze O’Toole said: “This is a significant pollution threat as there are nearly half a million domestic wastewater treatment systems in Ireland. Many rural homes lack connection to the main sewer. Instead, they have their own domestic treatment system to collect, treat and discharge their wastewater.

“It is often difficult for homeowners to know if their system is working properly because the tanks and soakaways are underground. People are unaware of where to turn for help to check and fix their septic tanks, or that they may qualify for financial support to carry out repairs.

“Homeowners need help because the improper maintenance of septic tanks can contaminate household wells, gardens, and bathing waters with harmful bacteria and viruses. Moreover, the release of nitrogen and phosphorus from septic tanks contributes to pollution in rivers and other water bodies.”

The EPA’s national inspection set targets for local authorities to inspect more than 1,000 waste-water systems every year. However, there has been a consistent failure rate of between 44 and 57 per cent since the inspections were brought in 10 years ago.

Constanze concluded: “Sadly, the dial hasn’t moved in the right direction in over a decade regarding leaking septic tanks in Ireland. We are failing to address this problem adequately, so river and water source pollution continues. This EPA report should be a wake-up call to address this issue, it needs coordinated and concerted efforts by all. We have an opportunity to remove a huge source of water pollution with relatively straightforward actions.

“The Rivers Trust calls for a collective effort from all domestic users to ensure their system is safe and functioning properly and for local authorities to advise and facilitate repairs. We also urge the government to take the lead with a strategy to educate and support people to ensure their systems are safe. We need concerted action to combat this alarming failure rate and protect water source and public health.”